Alexandra Lolavar studies how environmental factors, occurring inside the nest, determine sex ratios within the nests of marine turtles. Understanding this process is critically important for managing and conserving marine turtles so that the ratios of male to female hatchlings is appropriate and will be likely to promote the recovery of these threatened or endangered species.
Sea turtles have temperature dependent sex determination (TSD) - males are produced at cooler temperatures and females at warmer temperatures. While biologists remain confident of temperature’s role in sex determination, Lolavar’s studies have also identified moisture, in the form of rainfall, as another environmental factor that can modify sex ratios. Her experiments are designed to determine whether moisture alone, or the role of moisture as an agent of evaporative cooling, result in the production of more males. She is also interested in whether additional environmental factors, such as nest oxygen levels, also influence the ratios of males to females.
The fact that environmental factors have such an important impact on sea turtle development also means that the ongoing threat of climate change may be particularly worrisome. Sea turtle biologists anticipate that global warming might result in an overwhelming production of females; even less understood is how worldwide changes in precipitation that accompany global warming might also impact marine turtle sex ratios. These “unknowns” make studies such as Lolavar’s extremely important, as they can provide insights into how managers should respond if environmental changes begin to have adverse effects on marine turtle sex ratios.
Jake Lasala is interested in identifying the hidden elements of sea turtle behavior and population structure, those that determine the romantic relationships between males and females. The problem, from the perspective of an observer, is that how male and female marine turtles court and respond to one another occurs underwater, sometimes in deep water, and it’s only by the best of luck that human observers (let along those who are qualified biologists) get to witness what transpires. Even when they do see marine turtles mating, how can biologists be sure of the “result”? Mating may or may not be successful, especially when the offspring often number more than 100 hatchlings from a single nest. How many of those 100 are sired by a single male? If a female mates more often than once, a common occurrence in marine turtles, how many offspring are sired by different males? Many animals have similar (technically known as “promiscuous”) mating systems. In some of these species, all of the offspring are sired by the last male to mate with that female and none by those that mated with her earlier. Does that principle apply to marine turtles?
Lasala uses genetic markers from Mom and the hatchlings to answer these questions. The technique is essentially identical to the genetic methods used in lawsuits to determine paternity. Since each hatchling obtains half of their genes from mom and half from dad, you can use skin and blood samples from mom to identify her genes, and tiny amounts of blood from the hatchlings to identify her genes in each hatchling. Any unfamiliar genes found in the hatchlings must come from dad, and any different unidentified genes found in different hatchlings indicate that the hatchling had a different father.
By the end of the 2015 nesting season, Jake had sampled from over 135 nesting females and over 2,700 hatchlings from the three species that regularly nest on Florida’s beaches: the loggerhead, leatherback and green turtles nesting at three beach sites (Jupiter, Boca Raton and Sanibel, Florida). Each sample needs to be analyzed to determine paternity. Thus far, the results indicate that all species are promiscuous, but that loggerheads are more promiscuous than the other two species. Why that should be the case isn’t clear, and probably won’t be answered in this study. That’s a topic awaiting observations made by scientists who want to spend a lot of time underwater, watching the turtles make love. Jake, however, prefers to obtain his data by analyzing his tissue samples in the laboratory. To each, their own!